Poorly running 240

Poorly running 240 - Solved

I know these pop up often... sorry.

1993 244

I've had a weird intermittent issue where the car would run great for hundreds of miles then stall one day. Then run great again. Sometimes an occasional stumble and back to running good.

It eventually got worse and at times wouldn't start or it would start but not idle on it's on. Until it got bad I never had any codes. But once it wasn't driveable, I got the 1-1-3 faulty fuel injectors or incorrect fuel mixture depending on where you look up the codes.

I assumed I could figure it out with parts..

Main pump and filter. Also checked fuel pressure with only pumps running, car running and the car running with the FPR unplugged.

Replaced the powerstage and CPS.

Swapped plug wires.

New plugs - the old plugs were gapped way more than they should have been but the car ran great the last 25K with them.

Swapped in rebuilt Bosch injectors. Ohm tested new o-rings.

New ECT.

New o2 sensor.

I cleaned and made sure the idle control valve was clicking open.

Verified the injectors were firing.

Blew cigar smoke in vacuum hoses and blasted the engine with carb cleaner trying to find leaks with no luck.

After replacing the injectors and plugs it started much better but won't idle at all. Runs decent if I keep my foot on the pedal. It's pretty smooth but seems like a little bit of a hiccup. I had the battery unplugged so I guess that erased any codes. But the check engine light came on and I still have the 1-1-3 code.

I tried checking the O2 sensor at the computer plug and I did not see continuity. I checked the green wire from where it connects to the O2 harness and at the plug to the computer and I had continuity (assuming this means there's no break in the wire).

Any ideas on why I wouldn't have continuity for the O2 sensor? Same reading on the last sensor and replacing didn't fix it. And are there other ways to check it or anyone have any ideas I check?

An oxygen sensor generates a small voltage. You can use the continuity testing for the wiring. But don't test with the sensor connected. Ohmmeters generate a small voltage too.

Have you made sure the engine mechanically is ok to run? Like checking for a good timing belt? Make sure the distributor has numper one cylinder in the correct location?

The timing had crossed my mind but that wouldn't be an intermittent problem. I replaced the timing belt and tensioner around 25k ago and made sure to check the tension a few times.

It ran weird on day and I replaced the coolant temp sensor and it then ran like normal. I drove it around 3.5 hours over the next 2 days with no problem then it stalled.

I'll keep messing with it and report back when I figure it out to hopefully help someone else one day.

May try monitoring the idle air motor and AMM while idling with a meter, I had intermittent severe power loss, was fine for 1/2 tank of gas then lost all hp when accelerating. After firing the parts shotgun at the fuel system, it turned out to be the AMM and idle air motor had intermittent problems, the idle air motor was actually the main culprit, started sticking open when warm, but only every once and a while. It seemed to be worse the warmer the engine got, like sitting in traffic for extended periods of time.
Not exactly what you are experiencing, just throwing it out there

Got any rattling s#!t that might trigger the knock sensor? just tossin' it out there... I am not an expert.

Your 93.. is it the late production with the fuses on the battery post?

113 is telling you it is in limp-home rich mode and not about faulty injectors, and the continuity test prescribed in Bentley has an error where the oxygen sensor wiring is checked. Reset the computer by momentarily removing the FI fuse (either #6 inside or the PAL fuse outside if yours is late production) and monitor the oxygen sensor output voltage once it is warmed up. Before you reset the computers, it will run poorly but run. After you reset, give it 10 minutes to adapt again before you trust taking your foot off of the accelerator pedal for idle. My experience is rife with poor connections rather than "bad" parts. However a "bad" FPR or AMM or O2 will get the thing into limp-home 113 and make it feel intermittent.

when I discovered how correcded and damaged the battery terminal was under the late model fuse block. I was able to source a gold plated marine terminal from one of the local auto stores to replace only the battery terminal. The fuse block and battery cable bolted up to it and it's been more reliable since then.

2turbotoys said:

May try monitoring the idle air motor and AMM while idling with a meter, I had intermittent severe power loss, was fine for 1/2 tank of gas then lost all hp when accelerating. After firing the parts shotgun at the fuel system, it turned out to be the AMM and idle air motor had intermittent problems, the idle air motor was actually the main culprit, started sticking open when warm, but only every once and a while. It seemed to be worse the warmer the engine got, like sitting in traffic for extended periods of time.
Not exactly what you are experiencing, just throwing it out there

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Once I get it to idle I'll try that, thanks.
I just pulled the throttle body to clean it and reset the throttle switch. It was much dirtier than I thought it would be.

Hacksaw116 said:

Got any rattling s#!t that might trigger the knock sensor? just tossin' it out there... I am not an expert.

Click to expand...

Not that I know of but thought about swapping in a new one in since they are not too expensive.

cleanflametrap said:

Your 93.. is it the late production with the fuses on the battery post?

113 is telling you it is in limp-home rich mode and not about faulty injectors, and the continuity test prescribed in Bentley has an error where the oxygen sensor wiring is checked. Reset the computer by momentarily removing the FI fuse (either #6 inside or the PAL fuse outside if yours is late production) and monitor the oxygen sensor output voltage once it is warmed up. Before you reset the computers, it will run poorly but run. After you reset, give it 10 minutes to adapt again before you trust taking your foot off of the accelerator pedal for idle. My experience is rife with poor connections rather than "bad" parts. However a "bad" FPR or AMM or O2 will get the thing into limp-home 113 and make it feel intermittent.

Click to expand...

I'll try this also once I get the throttle body gasket. Thanks

I reinstalled the cleaned TB with new gasket and seal and made sure I heard the click. The car started fine and idled on its own with no prob but eventually gave the 1-1-3 code again. although it does idle own its own now, its idling a little low and not as steady as it should be. I tried to test the O2 sensor but a little confused on how to. Bentley says test the single wire (I assumed this was the connector to the thick green wire as the other connector has two wires), Haynes says to disconnect the electrical connector and connect the positive probe to the output signal.

I just replaced the O2 with a new Bosch 3 wire from FCP. It has the two wire connector (two white wires) and the single wire connector (black to the thick green wire).


So to be sure should I be getting the .4-.9V from the black wire? and should it be plugged in or unplugged? after letting the car warm up I tried to test the voltage there and got a .93-.95. If I'm testing it correctly I believe that means its just running rich and I guess that's in line with eh 1-1-3 code.

vwblue1967 said:

So to be sure should I be getting the .4-.9V from the black wire? and should it be plugged in or unplugged? after letting the car warm up I tried to test the voltage there and got a .93-.95. If I'm testing it correctly I believe that means its just running rich and I guess that's in line with eh 1-1-3 code.

Click to expand...

Yes, you should see the voltage on the black wire kick back and forth between about 0.2 and about 0.8V, switching between lean and rich respectively. The wire needs to be connected. That's how the O2 sensor keeps the average mixture correct.

When it switches below about 0.5V, the ECU is programmed to push more fuel, by lengthening the time the injector valve is open until the O2 reports above about 0.5V, when it will cut back that injector's open time. Like the thermostat in your home. Feedback.

So, if it reports a constant rich signal, something else is not allowing the system to shut down the fuel. The fuel pressure regulator could be faulty, allowing fuel to bypass it through a leak in its diaphragm, or rarely, if it is stuck shut. The air mass meter could be falsely reporting more air than is actually flowing through it, or poor corroded connections might corrupt its message to the ECU. The coolant temperature sensor could be trying to tell the ECU it is minus 40 in the head, or its signal is not being faithfully delivered to the computer.

After some time the ECU has given up trying to get a reaction from the oxygen sensor, and has simply forced a rich mixture to protect the motor, and set the 113 code. Then you'll see it stuck at 0.9V or thereabouts.

cleanflametrap said:

Yes, you should see the voltage on the black wire kick back and forth between about 0.2 and about 0.8V, switching between lean and rich respectively. The wire needs to be connected. That's how the O2 sensor keeps the average mixture correct.

When it switches below about 0.5V, the ECU is programmed to push more fuel, by lengthening the time the injector valve is open until the O2 reports above about 0.5V, when it will cut back that injector's open time. Like the thermostat in your home. Feedback.

So, if it reports a constant rich signal, something else is not allowing the system to shut down the fuel. The fuel pressure regulator could be faulty, allowing fuel to bypass it through a leak in its diaphragm, or rarely, if it is stuck shut. The air mass meter could be falsely reporting more air than is actually flowing through it, or poor corroded connections might corrupt its message to the ECU. The coolant temperature sensor could be trying to tell the ECU it is minus 40 in the head, or its signal is not being faithfully delivered to the computer.

After some time the ECU has given up trying to get a reaction from the oxygen sensor, and has simply forced a rich mixture to protect the motor, and set the 113 code. Then you'll see it stuck at 0.9V or thereabouts.

Click to expand...

Thanks for the info!

I was wondering how one would run rich, i thought the injectors pulsed on at a certain speed and maybe were firing too fast but you helped explain it happens from the injector valve being opened longer. cool now I know.

I have already replaced the coolant temp sensor and I tested the one that came out, I dont believe there was anything wrong with it either.

I removed the fuel rail, swapped in cleaned injectors with new seal and made sure the grounds were good. ive checked the engine bay grounds a few times. I removed the MAF sensor and cleaned it, i done believe theres any problems with the connector there or at the ECU, Ive had it off a couple of times trying to test ohms and continuity of different things.

When I removed the throttle body, i reset the switch but it doesnt make the "click" nearly as loud as the one on my 85 wagon. Could that be a symptom of anything? it clicks but its hard to hear in comparison to my other car....either way ill probably be trying a new (or good used)MAF sensor next. they fuel pressure seemed in spec with only the pumps running, the car running and with the car running and the vacuum hose disconnected. I was also able to blow through the return line to verify it wasnt clogged. It wasnt easy to do but i def heard the gurgling sound at the other end.

.9v, as mentioned, means stuck rich.

Try the measurement again on a hot engine and with the sensor unplugged. Measuring on the o2 sensor side. It makes it's own voltage.

Can't hurt to measure the resistance of each injector, disconnected. See if they are all similar.

Things that come to mind that would cause a rich condition would be torn FPR diaphragm, stuck open fuel injectors, bad computer, bad temp sensor, or bad MAF. About in that order.

ZVOLV said:

.9v, as mentioned, means stuck rich.

Try the measurement again on a hot engine and with the sensor unplugged. Measuring on the o2 sensor side. It makes it's own voltage.

Can't hurt to measure the resistance of each injector, disconnected. See if they are all similar.

Things that come to mind that would cause a rich condition would be torn FPR diaphragm, stuck open fuel injectors, bad computer, bad temp sensor, or bad MAF. About in that order.

Click to expand...

Now that the car will idle on it's own, I did the test the o2 voltage while it was hot. If I measure it unplugged, what do I unplug? All of it or just one of the connections?

I did test all injectors in and out of the car. All read 16 ohms.

If the FPR was bad would I still get the correct pressure readings? I have the 951 computer I believe. I would hope everything else would fail before the computer and from reading around but I guess it could. Temp sensor was replaced and the old one tested fine (going from freezer to in front of a heater). I need to find a good used MAF sensor and see what happens.

O2 has

1. Signal
2. Heater positive
3. Heater ground

update …

I swapped in a known working MAF sensor and after clearing the codes, no more check engine light. The car seems to run and drive fine now but a few times the idle jumped around (after I came to a stop). I have also noticed its taking a few seconds longer to start than it use to. Checking the diagnostics I now have a 2-3-2 code that I believe has to do with the mixture at idle. So I guess I'm still having issues with the A/F mixture. I checked the O2 sensor and verified the voltage jumping around. Ill keep messing with it until everything is running like it should and make updates.

Until I started having these problems, this car always started first time quickly and has never given any problems. It always idled right at 750rpm and hopefully ill get it back there soon.

2nd update

The problem seemed to be solved, I guess i had to drive it for a while. there are no longer any codes and the car seems to be back to normal.

It looks like the problem was the MAF sensor. I believe the sensor failed or was intermittently going bad causing the off an on problems I was having. Once the car went into limp home mode, it ran rich and fouled out the plugs. I noticed when I swapped in new plugs, the ones I had in the car were gaped way to big. It ran fine for 25K miles but it may not have been good when I was in limp home rich. After the new plugs it would idle but still had a code. When checking the the throttle body and TPS, I had prev only cleaned the TB with a rag but it was pretty dirty i removed it and cleaned it and installed a new throttle shaft seal. After swapping in a good used MAF sensor it got better again, still had a 1-1-3 code. drove it for a little bit (cleared the code) and got the 2-3-2 code with no check engine light. Drove it for another 20 or so miles and reset the code and have been driving fine with no engine light or codes. The car was taking a few seconds longer to start, that is due to the in tank pump. The harness broke off from the sender so there has been no power to the pump or gas gauge. i always fill up around the 220 mile range and it usually takes 9-10 gal to fill up. this time it took over 12. All of the running rich was really dumping the fuel out because i was only at 189 miles. Once i had a full tank it started up quickly like it should (new sender, sock, pump are on the way).
I know its not the best to just start replacing parts but i also like having a functional spare of everything.

so replaced the main pump and filter
power stage
plugs
injectors
coolant temp sensor
CPS
cleaned throttle body
checked for leaks 10xs
new O2 sensor
checked grounds
verified fuel pressure
and probably more I've forgotten about...but the main issue was the MAF sensor.